1. Field of the Invention
This invention relates to a data recording apparatus, and more particularly, to an apparatus for recording a data, sequence including main binary data formed by sampling a main information signal, and a plurality of subordinate binary data which respectively carry additional information of varied kinds.
2. Description of the Prior Art
In the following description, the present specification takes up, by way of example, a tape recorder of the kind wherein a magnetic recording tape is wrapped at a given angle around a cylinder which is equipped with rotary heads; and digital audio signals are recorded or reproduced, as main information, by means of the heads in or from a plurality of areas longitudinally arranged on the recording tape.
FIG. 1 of the accompanying drawings shows the tape transport system employed by the conventional tape recorder of the above-stated kind. FIG. 2 shows recording tracks formed on a tape by the tape recorder.
While the head 3 or 4 traces distances from a point A to a point B, from the point B to a point C, from the point C to a point D, from the point D to a point E, from the point E to a point F and from the point F to another point G, audio signals can be recorded in areas CH1 to CH6. These areas CH1 to CH6 thus can be used for recording different audio signals therein, respectively. An operation called azimuth-overwrite is performed on these areas. However, the tracks of these areas CH1-CH6 do not have to be on the same straight line. Each of the areas CH1-CH6 has one pilot signal recorded therein for tracking control. Different pilot signals are thus recorded in different areas in the order of rotation f1 f2.fwdarw.f3.fwdarw.f4. However, there is no correlation between them.
Referring further to FIG. 1, recording or reproduction is carried out in or from these areas CH1 to CH3 while the tape 1 is travelling at a predetermined speed in the direction of arrow 7, and in or from the areas CH4 to CH6 while the tape is travelling in the direction of arrow 9. Therefore, as shown in FIG. 2, the inclination of the areas CH1 to CH3 somewhat differs from that of the areas CH4 to CH6. With regard to a difference in the relative speed of the tape and the head for these groups of areas, a difference arising from the travel of the tape 1 is extremely small as compared with a difference arising from the rotation of the heads 3 and 4. Therefore, the difference in the relative speed presents no problem.
FIGS. 3(a) to 3(j) show, in a time chart, the recording or reproducing operation of the tape recorder which is arranged as described above. A phase detection pulse (hereinafter referred to as a PG signal) is generated in synchronism with the rotation of the cylinder 2 as shown at FIG. 3(a). The PG signal is a rectangular wave of 30 Hz repeating a high level (hereinafter referred to as an H level) and a low level (hereinafter referred to as an L level) alternately with each other at intervals of 1/60 sec. Another PG signal, which is of the opposite polarity to the PG signal of FIG. 3(a), is shown in FIG. 3(b). The first PG signal is at an H level while the head 3 is rotating from the point B to the point G of FIG. 1. The other PG signal shown in FIG. 3(b) is at an H level while the other head 4 is rotating from the point B to the point G.
Pulses for reading data are obtained from the PG signal of FIG. 3(a) as shown in FIG. 3(c). The data reading pulses are used for sampling the audio signal of a period corresponding to one field (1/60 sec). FIG. 3(d) shows, by H level parts thereof, periods provided for signal processing on the one field portion of the sampled audio data by adding an error correcting redundant code or by changing the arrangement thereof by means of a RAM or the like. FIG. 3(e) shows a signal indicating data recording periods at H level parts thereof which represent timing for recording, on the tape 1, the recording data obtained through the signal processing operation mentioned above.
Referring to FIGS. 3(a) to 3(j), the temporal flow of signals are, for example, as follows: The data sampled during a period from a point of time t1 to a point of time t3, i.e. while the head 3 is moving from the point B to the point G, is subjected to a signal processing operation during a period from the point of time t3 to a point of time t5, i.e. while the head 3 is moving from the point G to the point A and are then recorded during a period from the point of time t5 to a point of time t6, or while the head 3 is moving from the point A to the point B. In other words, the data is recorded by the head 3 in the area CH1 as shown in FIG. 2. Meanwhile, the data which is sampled while the PG signal of FIG. 3(b) is at an H level, is also processed at a similar timing before it is recorded in the area CH1 by the head 4.
FIG. 3(f) shows another PG signal which is obtained by shifting the phase of the PG signal of FIG. 3(a) to a predetermined degree, which corresponds to one area, and is 36 degrees in this specific instance.
An audio signal recording operation using the PG signal of FIG. 3(f) and a PG signal which is not shown but is of an opposite polarity to the former is performed in the following manner: The data which is sampled during a period between the points of time t2 and t4 is subjected to a signal processing operation during a period between the points of time t4 and t6 in accordance with the signal of FIG. 3(g) and is recorded during a period between the points of time t6 and t7 in accordance with the signal of FIG. 3(h). In other words, the data is recorded in the area CH2 of FIG. 2 while the head is moving from the point B to the point C. Meanwhile, another data which is sampled during the points of time t4 and t7 is likewise recorded in the area CH2 by means of the other head during a period between the points of time t4 and t7.
The signal which is recorded in the area CH2 in the manner as described above is reproduced in the following manner:
The head 3 reads the data from the tape 1 in accordance with a signal shown in FIG. 3(h) during the period between the points of time t6 and t7 (and also during the period between the points of time t1 and t2). Then, during the period between the points of time t7 and t8 also (between t2 and t3), the reproduced signal is subjected to a signal processing operation which is carried out, in a manner reverse to the signal processing operation performed for recording, in accordance with a signal shown in FIG. 3(i). In other words, error correction and other processes are carried out during this period. Then, during a period between points of time t8 and t9, the reproduced audio signal which has been thus processed is produced in accordance with a signal shown in FIG. 3(j). The reproducing operation of the head 4 is of course performed with a phase difference of 180 degrees from the above-stated reproduction by the head 3, so that a continuous reproduced audio signal can be obtained.
For other areas CH3 to CH6, it goes without saying that the recording and reproducing operations are performed on the basis of the PG signal of FIG. 3(a) by phase shifting it as much as n.times.36 degrees. This is independent of the travelling direction of the tape.
An example of the conventional data formats employed for the apparatus of the above-stated kind is as follows: FIG. 4 shows a data format for data to be recorded within each of the recording tracks formed in each of the areas shown in FIG. 2. In other words, in this format, the data includes the PCM audio data which corresponds to a 1/60 sec. portion of a two-channel audio signal.
In the data matrix of FIG. 4, a column SYNC represents a data train for synchronization. A column ADDRESS represents an address data train. Columns P and Q represent redundant data trains for error correction. A column CRCC represents a CRCC check code data train. Columns D1 and D2 respectively include a plurality of columns. The plurality of columns of each of the columns D1 and D2 carry audio signal information of two channels. Meanwhile, lines b(0) to b(3x-1) represent the lines of the data matrix. Each of these lines forms one block of data, which are recorded one after another from the left-hand side to the right. For example, the data of the coloumn ADDRESS in the line b(0) is recorded next to the data of the column SYNC in the line b(0) and is then followed by the data of the column P in the line b(0). Further, the data of the last column in the line b(x) is followed by the data of the column SYNC in the line b(x+1). Data recording for one track is completed when the data of the last column in the line b(3x-1) is recorded.
The six data ID0 to ID5 of the first column among the plurality of columns D1 in lines b(0), b(1), b(x), b(x+1), b(2x) and b(2x+1) corresponds to additional information other than the information of the audio signal. Hereinafter, these six data will be called ID data.
In the field of the art of recording digitized information signals on recording media, the technology for data recording in a high degree of density is advancing. The advanced technology has come to allow a greater latitude for the data format to be employed in recording data on the medium. As a result, recording apparatuses for recording data in similar recording formats have come to be compatible. Therefore, for interchangeability among them, it is preferable that information about the recording format employed be recorded in some suitable form on the recording medium. Further, with the high density recording having become possible, it has become feasible to record an analog information signal over an extremely long period of time. Hence, it is also preferable to have information about time and programs likewise recorded. Since the analog information signal is to be recorded in the form of digital data, it is advantageous to have the above-stated time and program information recorded on the recording medium also in the form of digital data consisting of the same number of bits as the information signal, because such arrangement does not hinder the high density recording arrangement. The above-stated ID data is recorded on the basis of this concept.
These ID data are intended not only to be reproduced in carrying out normal reproduction, but also to be used for other purposes. The data for look-up and the data indicative of time information are often required to be quickly picked up by allowing the tape to travel at a high speed. However, with the tape allowed to travel at a high speed, it becomes hardly possible to have all these ID data reproduced in exactly the same state as they are recorded because of deviation of the tracing locus of the rotary head from recording tracks. FIG. 5 shows this.
Referring to FIG. 5, a reference symbol S1 denotes the tracing locus of a rotary head of plus azimuth and a symbol S2 the tracing locus of a rotary head of minus azimuth. Oblique full lines represent boundary lines between recording tracks. Symbols X, Y and Z denote the recorded positions of the above-stated data ID0 and ID1, the data ID2 and ID3 and the data ID4 and ID5. Hatched parts represent the parts of the recording tape from which reproduction outputs are obtained.
As is apparent from FIG. 5, the ID data are reproduced from different recording tracks by one stroke of tracing. Meanwhile, the kinds of information desired to be added in the form of the ID data are trending to increase in number. To meet this trend, it has been attempted to contrive different modes of recording these ID data. However, with one of such different recording modes applied to the data ID0 to ID5, if the mode varies at every track, the meaning of four ID data would become hardly discernible when the tape is allowed to travel at a high speed. While FIG. 5 shows an ideal tracing locus, sometimes it would be possible to reproduce only some of the ID data recorded in the positions X, Y and Z depending on the travelling speed of the tape.
Further, while all the look-up data of the above-stated kind are preferably recorded in one and the same ID data recording mode, such arrangement does not allow any increase in the amount of additional information as the amount of information recordable in a single recording mode is limited. To solve this problem, use of a sub-recording mode is conceivable. However, even according to that method, it sometimes becomes difficult to adequately discern necessary information depending on the travelling speed of the tape. Besides, adoption of that method would result in a further decreased number of bits usable for recording additional information.